1. Field of the Invention
Maitake in Japanese [Grifola frondosa (Fr.) (pers. ex Fr.)] (a kind of mushroom) is a source of vegetable proteins and edible fiber. Additionally, it has been reported recently that xcex2-glucans in Maitake exerts various pharmacological effects such as anticancer effect, dementia-preventing effect, immune enhancing effect, tumor-suppressing effect, hair-growing effect and blood glucose-decreasing effect. In Japan and USA, dosage forms using Maitake as a raw material have been marketed already as nutritious supplements and health food products. Additionally, it has been known that Yamabushitake in Japanese [Hericium erinaceum (Bull. ex Fr.) Pers.] (an another kind of mushroom) also contains a lot of xcex2-glucans. Like Maitake, research works for the application of Yamabushitake to nutritious supplements and health food products have been under way. For such purposes, dosage forms using extracts (hot-water extract or alkali hot-water extract further fractionated and purified as so-called D-fraction) of Maitake or Yamabushitake is general. It is said that by the extraction, components with particularly excellent pharmacological effects in xcex2-glucans can be concentrated greatly. According to recent research works, however, concomitant dosing of xcex2-glucans and the proteins in the mushroom further enhances the pharmacological effect of xcex2-glucans. By the hot-water extraction method or alkali hot-water extraction method, most of the proteins and fiber in the mushroom remains in the extraction residue, with the resultant less quantity in the extract.
2. Description of the Related Art
So as to effectively utilize xcex2-glucans in Maitake and Yamabushitake but also the vegetable proteins and fiber therein, research works for preparing Maitake or Yamabushitake as they are as dry powder have made a progress. However, Maitake and Yamabushitake emit unpleasant odor when dried, and when prepared into powder as they are, the odor is enhanced more. This is a serious drawback for merchandising and marketing Maitake powder or Yamabushitake powder as health food products.
It is a purpose of the present invention to provide a method for preparation of a deodorized mushroom powder from the fruit body of Maitake or Yamabushitake, particularly a deodorized mushroom powder containing not only xcex2-glucans but also proteins and fiber abundantly in a convenient manner and at low cost.
The method for preparation of a deodorized mushroom powder according to the invention comprises immersing the fruit body of Maitake or Yamabushitake in a heated aqueous acid solution, followed by drying and grinding.
The powder of the fruit body of Maitake or Yamabushitake as recovered by the method is with significantly reduced unpleasant odor. xcex2-glucans are transferred to the extract when the fruit body is immersed in hot water or alkali hot water. However, xcex2-glucans are never transferred to the extract when the fruit body is immersed in aqueous acid solution but is recovered as solid. The proteins and fiber are also recovered as solid. Furthermore, it has been found that the dried powder of the fruit body of Maitake or Yamabushitake as recovered in accordance with the invention is at a significantly large bulk density, compared with the powder dried with no acid treatment of the fruit body of Maitake or Yamabushitake.
As the aqueous acid solution, use is made of aqueous inorganic acid solution or aqueous edible organic acid solution. The inorganic acid includes hydrochloric acid, sulfuric acid, and phosphoric acid; the edible organic acid includes acetic acid, citric acid, malic acid, tartaric acid and succinic acid. In any of the cases, deodorizing effects can be observed. From the viewpoint that the products must be edible and from the viewpoint of working environment and liquid waste disposal problem, edible organic acids are preferably used. Among edible organic acids, acetic acid or citric acid is preferable in terms of cost and effect. As such acetic acid, use can be made of synthetic acetic acid, brewed vinegar, and fruit vinegar such as wine vinegar, papaya vinegar and apple vinegar.
The concentration of aqueous acid solution varies, depending on the kind of the acid used. When organic acids such as acetic acid and citric acid are used, the concentration thereof is preferably within the range of 0.01 to 1%. Below 0.01%, the deodorizing effect is less; and xcex2-glucans may leak into the immersion solution. From the viewpoint of deodorizing effect, the upper limit of the acid concentration is with no specific limitation. From the respect of the volume of water for washing after immersion treatment and work, the upper limit of the acid concentration is appropriately about 1%. The acid concentration of an inorganic acid to be used is satisfactorily lower than the acid concentration of an organic acid to be used.
The temperature of the aqueous acid solution is appropriately within the range of 40xc2x0 C. to 100xc2x0 C. Below 40xc2x0 C., the immersion time gets longer, involving the reduction of operability. Above 100xc2x0 C., a pressurized container is required for such immersion, involving higher equipment cost and reduced operability.
The immersion time in the aqueous acid solution varies, depending on the kind of acid, concentration and temperature of the aqueous acid solution and depending on the size of cut pieces of Maitake and Yamabushitake. Preferably, the range is within 10 minutes to 30 minutes. For 10 minutes, the deodorizing effect can be observed; for 30 minutes, almost complete deodorization can be attained. Accordingly, no more immersion is then required.